1. Field of the Invention
This invention relates to magnetohydrodynamic (MHD) apparatus, and more particularly provides arrangements for electrodes and walls in the plasma transmitting generator channel.
2. Description of the Prior Art
In MHD generators for large scale power generation, it is important for overall plant efficiency to keep the heat loss to the walls low, preferably less than one-half megawatt per square meter. If such losses exceed about one megawatt per square meter, the adverse effects on overall plant efficiency considerably diminish the attractive features of an MHD process. In order to reduce the wall heat losses, it is important to operate the MHD generator channel with hot walls, for example, walls with the channel internal surfaces running at an average temperature over 1600.degree. C.
Operation with hot walls provides other advantages, including the ability to run the generator walls cleaner and more free from seed and slag deposits, as compared to cold wall operation. Additionally, where hot walls are utilized, current collection to the electrodes tends to take place with the alleviation of arc spots, which spots have been found to occur in cold wall operations, thereby damaging the electrodes and supporting structures. Further, operation with hot walls reduces the cooling requirements for wall elements. Additionally, in order to further alleviate arcing and detrimental Hall effects, when cool walls are used, it is desirable to break up the electrodes into a large plurality of small electrodes, as opposed to larger electrode configurations.
It is therefore desirable to provide wall and electrode constructions for MHD generators which allow operation with hot wall surfaces and which further alleviate Hall effects and detrimental arcing and seed and slag deposits.